Turtle, Alligator Snapping

Macroclemys temminckii

Average adult length: 26 in (66 cm); average adult weight: 175 lbs. (80 kg); appearance & coloration: large, heavy head, and a long, thick shell with three dorsal ridges of large scales (scutes) with three distinct rows of spikes and raised plates on the carapace (shell); solid gray, brown, black, or olive-green in color, and often covered with algae. The tail is almost as long as the shell itself and, together with the chin, throat and neck, is coated with long, pointed tubercles (small wart-like or angular swellings). They have radiating yellow patterns around the eyes, which are also surrounded by a star-shaped arrangement of fleshy filamentous “eyelashes.” Male and female can be differentiated by the position of the cloaca from the carapace and the thickness of the tail’s base. A mature male’s cloaca extends beyond the carapace edge; a female’s is placed exactly on the edge if not nearer to the plastron. The base of the tail of the male is also thicker as compared to females because of the hidden reproductive organs.

Range

Habitat

Freshwater systems - deep water of large rivers, canals, lakes and swamps, though hatchlings and juveniles usually live in small streams.

Life Expectancy

Potential lifespans in the wild are unknown, but they are believed to be capable of living up to 150 years. In captivity, they typically live anywhere from 20-70 years.

Sexual Maturity

About 12 years

Diet

In the wild, they eat fish, invertebrates, carrion, and amphibians, but they are also known to eat snakes and other turtles; in the Zoo, they are fed a scientifically developed, keeper prepared meat sausage, rodents and fish.

Status

IUCN – Vulnerable, CITES – Appendix III

Behaviors

The alligator snapping turtle is a solitary species that seldom leaves the water. Nesting females venture onto land to lay their eggs, and males may venture out of the water to bask. The alligator snapping turtle actively forages for food at night, but is more of a ‘sit-and-wait’ predator during the day. The turtle lies quietly on the mud bottom with its jaws wide open, its dark coloring and its coating of algae making it almost invisible to fish. The worm-like lure within the turtle’s mouth is wiggled to entice unwary fish and, when the unlucky prey comes close, the turtle’s jaws are quickly snapped shut. These turtles stay submerged for 40 to 50 minutes at a time and only go to the surface for air. They are so motionless under water that algae can cover their backs and make the turtles almost invisible to fish. A study by Riedle et al. (2006) in Oklahoma radio-tagged adult turtles, and found that they prefer areas with submerged cover (logs, overhanging shrubs, occasional beaver dens) combined with high percentage of overhead canopy. The study also suggested that turtles thermoregulate using differing stream depths seasonally. For example, they chose deeper water during midwinter and shallower water in the early summer months. Mating takes place yearly; early spring in the southern part of their range and later spring in the north. During mating, male alligator snapping turtles mount the back of the female. He grasps her shell with all four feet to inseminate. The female builds a nest and lays a clutch of 10–50 eggs about 2 months later. Nests are typically excavated at least 50 yards from the water’s edge to prevent them from being flooded and drowned. Incubation takes from 100 to 140 days, and hatchlings emerge in the early fall. Alligator snapping turtle hatchlings look very similar to adults. Sex is determined by incubation temperature. Warm temperatures of 84 - 86°F (29 - 30°C) produce 100% females, while slightly lower temperatures 77 – 80.6°F (25 - 27°C) yield predominantly males. All other temperatures allow both to develop. Eggs are fertile if they have a clear subgerminal space or if a chalky white spot is on the eggshell. Though their potential lifespans in the wild are unknown, alligator snapping turtles are believed to be capable of living to 150 years of age but 50 to 80 is more likely. In captivity, they typically live from anywhere between 20 to 70 years of age.

Adaptions

The inside of the turtle’s mouth is camouflaged, and it possesses a vermiform (literally, “worm-shaped”) appendage on the tip of its tongue used to lure fish. The turtle hunts by lying motionless in the water with its mouth wide open. The vermiform tongue imitates the movements of a worm, luring prey to the turtle’s mouth. The mouth is then closed with tremendous speed and force, completing the ambush. Alligator snapping turtles use chemosensory cues to locate prey items. They use gular (throat) pumping to draw water in and out to sample the surrounding water for chemicals that have been released by prey species. Adult snapping turtles use this sensory system to hunt and locate mud and musk turtles that have buried themselves into the mud bottom of a body of water.

Special Interests

The alligator snapping turtle (Macrochelys temminckii) is one of the largest freshwater turtles in the world. It is a larger relative of the common snapping turtle. The species name, temminckii, is in honor of Dutch zoologist Coenraad Jacob Temminck (1778 – 1858), the first director of the National Natural History Museum at Leiden from 1820 until his death. Unlike the family Chelydridae as a whole, the genus Macrochelys is exclusively North American and is generally considered to contain three valid species: the extant M. temminckii and the extinct M. schmidti and M. auffenbergi (described from the early middle Miocene of Nebraska and the middle Pliocene of Florida, respectively). The only known predators of adults are humans, but eggs and hatchlings are a source of food for large fish, raccoons, and birds.

Folklore

There are many myths about alligator snapping turtles attacking, even killing, humans; none of which are true (Pritchard, 1989). However, their strong jaws and sharp beaks make them potentially dangerous if carelessly handled. Pritchard (1989) verified that persons have had their fingers severed away cleanly; additionally, he demonstrated that the jaws of an alligator snapping turtle are formidable enough to break completely through the handles of the “flimsier” variety of brooms sold in today’s supermarkets.

Conservation

The alligator snapping turtle is primarily vulnerable to humans from habitat loss and hunting. Some are hunted for their carapaces; the plastron of the turtle is valued because of its shape as a cross. There are accounts of large (50+ lb) turtles being caught both purposely and accidentally on recreational fishing lines called “trot lines.” Abandoned trot lines are thought to be even more dangerous to turtles. Soup made from snapping turtle meat is considered by some to be a delicacy. Collecting wild specimens is prohibited in Arkansas, Florida, Georgia, Indiana, Missouri and Tennessee, but allowed with the necessary permit in Alabama, Illinois, Kansas, Louisiana, Oklahoma and Texas. The alligator snapping turtle has been found in reservoirs throughout its range, and diking of rivers to create winter waterfowl refuges has increased the available habitat in Arkansas and the lower Mississippi Valley, which may help offset some of the habitat degradation and loss seen elsewhere. The species range is greater than 10,000 km² but population densities are likely to be low throughout this area (Ewert 1997). It is naturally rare in northern extremes of its range. Klemens and Behler (1997) reported that there is good anecdotal evidence that the species is undergoing a long-term, noncyclical decline throughout much of its range. The main threats include habitat alteration; exploitation by trappers for a large domestic market and a growing international market for its meat; pollution and pesticide accumulation.

Jacksonville Zoo History

Jacksonville’s first recorded alligator snapper arrived about 1963 and we had them on our inventory until 1982. The species was added again in 2009.